Does Maryland law require that experts rely upon epidemiology to establish medical causation in a toxic exposures personal injury case? In Sugarman v. Liles, decided on July 31, 2018, the Maryland Court of Appeals strongly implied that this was so, which may have fundamental implications for toxic tort cases going forward in the state.  No. 80, Sept. Term, 2017, 2018 WL 3642143 (Md. July 31, 2018).
 
The Court of Appeals in Sugarman wrestled with whether a pediatrics and childhood lead poisoning expert witness in a lead paint case had a sufficient factual basis to testify that lead exposure can cause certain attention problems. Because the expert relied on epidemiological studies that recognized a causal link between lead exposure and attention problems, no “analytical gap” was present, and the Court of Appeals therefore upheld the trial court’s allowance of the expert’s testimony.
        
The high court spent significant time discussing epidemiology, i.e., “the field of public health and medicine that studies the incidence, distribution, and etiology of disease in human populations.” The Court of Appeals recognized that epidemiology finds associations, or a relationship among variables. For instance, in an outbreak of salmonella, if a group of patients reports having eaten at a particular restaurant, there is an association between the salmonella outbreak and that restaurant.  

The Court of Appeals reasoned that inferring “causation from associations . . . requires identifying and controlling for potential confounding factors to rule out alternative explanations for an association.” Thus, even though there is an association between the restaurant and salmonella, it could very well be that that restaurant is merely popular, served safe food, and had nothing to do with the outbreak.  

In Sugarman, the Court of Appeals focused on the study the challenged expert had relied upon: the U.S. EPA’s Integrated Science Assessment for Lead (the “ISA”). The Court found the ISA to be a document that had ‘reviewed, synthesized, and evaluated other scientific studies and research” published by others. The EPA “scrutinized the evidence, received peer input, and ultimately evaluated the weight of that evidence to reach conclusions about causal determinations or the lack thereof.”  

The EPA was cognizant of the limitations of its study: it recognized that, for some exposures, it could only find an association between lead exposure and symptoms, but for other exposures, it might find a cause. If the EPA found a symptom to be caused by lead exposure, that meant the lead “has been shown to result in health effects in studies in which chance, bias, and confounding could be ruled out with reasonable confidence.” This evidence would need to include “multiple high-quality studies.”

The EPA identified a causal relationship between attention deficits and exposure to lead. The expert testified that the Plaintiff had suffered from generalized attention deficits. Therefore, the Court of Appeals held that the expert’s testimony did not suffer from an analytical gap, and upheld the trial court’s admission of the evidence.

Going forward, however, the Court of Appeals appears to have endorsed the idea that well-controlled epidemiological analysis is necessary to establish causation in a toxic tort case. In a prior lead paint case, Rochkind v. Stevenson, the Court of Appeals found that an expert who also relied upon the ISA to establish causation between lead exposure and Attention Deficit Hyperactivity Disorder (or “ADHD”) was unable to do so under Maryland Rule 5-702 because that expert’s analysis suffered from an analytical gap. Specifically, the Rochkind Court determined that the ISA only revealed an association between lead paint exposure and ADHD. Whether the Court of Appeals will require experts to explain away confounding factors in other toxic exposure cases remains to be seen, however.     

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